Laboratory hood apparatuses of varying configurations are widely known in the prior art. Commonly used in laboratories in both educational institutions and in diverse industries, e.g. chemical, medical, and pharmaceutical industries, laboratory hood apparatuses provide an operator with access to a work chamber for performing various scientific tests, reactions, and experiments while protecting the operator and the ambient laboratory environment from exposure to potentially dangerous contaminants. Such contaminants, including toxic or noxious fumes or reaction byproducts in the form of gases or vapors, produced within the work chamber of the apparatus are eliminated by filtration.
In its basic form, a conventional ducted laboratory hood apparatus has a work chamber which is substantially enclosed, but which includes an access window sufficient for an operator to reach in and perform laboratory processes within the work chamber. An air circulation system draws the air within the work chamber through at least one filter before it is vented through exhaust ducts to the air outside the building. Thus hazardous materials may be handled safely without endangering the operator or others in the workspace.
Such conventional ducted systems do, however, present several drawbacks, including energy inefficiencies, high installation costs, and lack of flexibility with repositioning. In order to address these concerns, ductless laboratory hood apparatuses have been developed. These ductless systems filter the contaminated air produced within the work chamber through use of an air circulation system which functions by using a fan to continuously withdraw air from the work chamber, passing the air through a filter of sufficiently high efficiency and capacity to render the air safe for human consumption, and then returning the air to the ambient laboratory environment.
Known prior art ductless laboratory hood apparatuses provide various advantages over the conventional ducted systems. Significant energy savings are achieved, as heated or cooled air within the room, having been cleaned of contaminants through the ductless laboratory hood apparatus, is returned to the work area. Additionally, ductless laboratory hood apparatuses provide significant flexibility in installation requirements. Costly construction of exhaust ducts is avoided and even after installation, the ductless fume hood may be relatively easily repositioned.
Despite their numerous advantages, ductless fume hoods known in the prior art are still faced with disadvantages, namely limitations presented by available filters having the requisite efficiency to produce air that is safe for human consumption upon its filtration from the work chamber area.
Filter materials conventionally used in both ducted and ductless fume hoods may be formed of a variety of materials for optimal performance in the filtration of various contaminant materials. Most commonly, activated carbon filters are used with ductless fume hoods known in the prior art. While effective in eliminating contaminants, these filters provide a significant disadvantage in that the material of which they are comprised is flammable and, under certain conditions, spontaneous ignition may occur. As various heat sources are necessarily used routinely in experiments and reactions carried out in a laboratory hood apparatus, the flammability of the filter requires that it be disposed a significant distance from any heat sources. This results in conventional ductless laboratory hood apparatuses that are very tall and, therefore, less flexible in installation.
Any filter which is to be disposed closer to a heat source within a laboratory hood apparatus must be sufficiently chemically resistant, provide efficient heat absorption, maintain a specified minimum pressure drop, and filter particles of a particular size.